K. Hagino & H. Okada: Observations of Gephyrocapsa crassipons, p. 3-7.

MORPHOLOGICAL

Journal of Nannolankton Research, 23, I, 2001.

OBSERVATIONS OF LIVING GEPHYROCAPSACRASS/PONS

Kyoko Hagino· & Hisatake Okadat*Shinjuku Branch, National Science Museum, 3-23-1 Hyakunin-chyo, Shinjuku-Ku Tokyo, 168-0073 Japan;
hagino@)whaku.go.jp
fDivision of Earth & Planetary Sciences, Graduate School of Science, Hokkaido University, N10 W8 Sapporo,
060-0810 Japan; oka@ep.sci.hokudai.ac.jp

Abstract: The morphology of Gephyrocapsa crassipons was studied under an SEM, and was comparedwith that of Gephyrocapsa ericsonii and Reticulofenestra parvula var. tecticerltrum. G. crassipons can be
distinguished from G. ericsonii and R. parvula var. tecticentrum by possessing a combination of overcalcified
inner tube and small distal shield, and dextrally-oriented bridge-plates, respectively.

Introduction
Gephyrocapsa crassipons, which was originally reported
as Gephyrocapsa sp.A from the tropical central Pacific
Ocean (Okada & Honjo, 1973), bears small placoliths with
two thick bridge-plates constructed of several elements,and a thick collar surrounding a central colunm (Okada &Mclntyre, 1977). Okada &Honjo (1973) reported that thisspecies formed upto 20% of the coccolithophore flora in
the tropical Pacific Ocean. The species, however, has notbeen recorded in subsequent studies, and there exist no
supplementary taxonomic studies based on SEM
observations. The reason why G. crassipons has not beenrecorded in the studies of the last 24 years is possibly
because all the authors have regarded G. crassipons assynonymous with other, better-known species (Jordan etal.,2000).
Throughout our recent studies of thecoccolithophore flora in the tropical and subtropical Pacific
Ocean, G. crassipons occurred commonly. Here, we present
SEM observations of G. crassipons, and compare themwith those ofGephyrocapsa ericsonii andReticulofonestra
parvula var. tecticentrum, species with similarly minutecell-size.

Cruise CodeStationLocation

Leg 9 of R/V Conrad
Leg 10 of RJV Conrad

66A

J7'33'S
05"40'N
03'31'N
12' 19'S
10' 23'S06' 60'S
03' 22'S04' 00'S
05' 59'S
09' 09'S
08'48'S!! ' 26'SJ3' 19'S!! ' 36'S
08' 17'S
19' 20'N
02'37'N
06'33'N
07'30'N
04'30'N
02' 20'N
06' 15'N
OJ ' 25'N
01 '43'N
01 '49'N
01 '46'N
01 '40'N
01 ' 54'N
01 ' 5i'N
02' 05'N
06' 15'N
02' 50'N
03' 04'N
03'45'N
J6'47'N

Leg 11 of RN Conrad

Leg 12 of R!V Conrad

139
142
121
122
123
124
125
126
127
128
129
130
131
132
4066
68

Leg 24 of RJV Vema

81
82
84
26
29
3132
33
34
35
36
37
38
39
40
41
44

Date

73' 09'W
127'20'W
129'43'W
136' 57'W
134'57'W
122' 30'W
122' 06'W
117'53'W
IJ5'37'W
113' 00'W
110'48'W
106'50'W
100' 57'W
95' 38'W
87' 46'W105' 12'W
148'53'W
149'02'W
164' 60'W
165'02'W
165' J2'W
90'40'W
JOO'J8'W
106'54'W
112'44'W
117' 12'W
J20' 20'W
124' 29'W
129'01'W
134'43'W
138'49'W
149' 52'W
155'35'W!57'07'W!56' 09'W

Feb. 5Mar. 6
Mar. 7
Sep. 12
Sep. 24
Sep. 26
Sep. 28
Sep. 31
Oct. I
Oct. 2
Oct. 3
Oct.5Oct. 7
Oct. 9Oct. 12
Feb. 23
Mar. 11Mar. 13
Apr. 2
Apr. 3Apr. 4
Feb. 25
Feb. 28
Mar. 2Mar. 4
Mar. 5Mar. 6
Mar. 7Mar. 8Mar. 10
Mar. 11Mar. 14Mar. 15
Mar. 16Mar. 21

1%919661966
1%71%71%71%71%71%71%71%71%71%71%71%71%8
1968
1%81968
1968
1968
.J%7
1%7
1%71%7
1%71%71%71%7
1%7
1%7
1%7
1%71%71%7

Material and methods
A set of filtered surface-water samples, collected from theequatorial and subequatorial Pacific Ocean by Dr. Andrew
Mclntyre (formerly at Lamont-Doherty Earth Observatory)
on various legs of RIV Conrad and RIV Vema, wereexamined to study the surface distribution ofcoccolithophore floras in the equatorial and subequatorial
Pacific Ocean. As a result of this floral investigation, a
total of35 samples were found to contain Gephyrocapsa
crassipons (Table 1).
The water-samples were filtered on-board using
Millipore filters (47mm diameter, normal pore-size of0.8J.U11)
and were dried at room temperature. Filters were stored inplastic Petri dishes. A portion of each filter was mounted
on a brass stub. Samples were sputter-coated with platinum
and examined under an SEM.

water is eutrophic due to upwelling (Hagino & Okada, inprep.). The highest absolute and relative abundances ofG. crassiponswere 1.7xl04 cells perlitre (St.l29, Leg 11 ofRIV Conrad) and 34.7% (St.l30, Leg 11 of RIV Conrad),respectively.

Observations of Gephyrocapsa crassipons
Gephyrocapsa crassipons (Plate 1, Figures 1-4) occurredin the eastern tropical Pacific Ocean where the surface-. Terminology
Okada & Mclntyre ( 1977) described the inward thickeningof the inner tube-wall of Gephyrocapsa crassipons as aTable 1: Water samples yielding Gephyrocapsa crassipons.

3

Journal of Nannolankton Research, 23 , I , 200 I .

K. Hagino & H. Okada: Observations of Gephyrocapsa crassipons, p. 3-7.

1, Figures I , 4). Therefore, the combination of centripetal
thickening of the inner tube and low-profile bridges, rather
than the number of elements composing a bridge-plate,should be the criterion to distinguish G. crassipons fromG. ericsonii .
Some of the collar elements of R. parvu/a var.
tecticentrum protrude centrally (Plate 1, Figure 6, arrows),
and they sometimes converge in the central area causing asimilar appearance to the bridge-plates of G. crassipons(Plate l , arrow (a) in Figure 7). The bridge-plates of G.
crassipons, however, can be distinguished from theovergrown collar-elements ofR. parvu/a var. tecticentrum
because the fonner span the central area diagonally with adextral offset (Plate 1, Figures 1-4 ), whereas the latter span
the central area in irregular orientations (Plate 1, arrows in
Figure 6 and arrow (a) in Figure 7). The inward overgrowthof the inner tube of G. crassipons sometimes covers thecentral area completely (Plate 1, Figure 4, arrow), giving asimilar appearance to the highly-overgrown R . parvu/avar. tecticentrum (Plate 1, arrow (b) in Figure 7 andcoccoliths of Figure 8). However, the embedded bridge ofan overcalcified G. crassipons protrudes, and can be clearly
distinguished from overgrownR. parvu/a var. tecticentrum,.
which has a flat or depressed central area (compare Plate 1,Figure 4 with Figure 8).
Both G. crassipons and R. parv u/a var.
tecticentrum are characterised by a highly-calcified inner
tube-structure, and occurred only in the samples from theequatorial upwelling zone, in the tropical and subtropical
Pacific Ocean (Okada & Honjo, 1973; Hagino & Okada, inprep). The inward expansion of the inner tube-structure ofthese two species, a feature of overcalcification, is likely
to be related to a particular eutrophic condition associatedwith tl1e equatorial upwelling system.

'collar' . In this paper, we substitute the term ' inner tube'
for 'collar' because this feature grows centrally notvertically in G. crassipons.
Description of coccosphere
The monomorphic, spherical coccosphere consists of 10
to 25 interlocked placoliths. Coccosphere size varies from2. 5 to 3.8 1ffi1 in diameter.
Description of coccoliths
The placolith is elliptical in plane-view, convex distally,concave proximally. The length ranges from 1. 3 to 2.3 J.l.lll,
and the width from 1.0 to l.8J.un. The distal shield is thesame size as the proximal shield, or slightly smaller (Plate 1,Figure 1, arrows). The proximal side of the central area iscovered by a grill or a perforated plate. The distal side
consists of the distal shield and inner tube. The proximaland distal shields are formed of radially-arranged, equal
numbers of elements, ranging between 20 and 30 in total.
Due to the centripetal overgrowth, the general form ofthe
inner tube varies even within a single coccosphere :fractured (Plate 1, Figure 2), expanded inwards to makebridge-like features (Plate 1, Figures 1, 3), or covering thecentral area completely (Plate 1, Figure 4, arrow) . Etched
specimens expose dextrally-rotated tube-core elements
between the distal shield and inner tube (Plate 1, Figure 2,arrow). The number of the tube-core elements is equal tothat of the proximal and distal shield elements. The bridgeplates span the central area diagonally with dextral offset.
The nmnber of elements fonning a bridge-plate ranges from
one to three, and is not consistent even within a single
coccosphere. The horizontal angle of the bridge varies
greatly, but the vertical projection is always maintained in
low profile. The junction ofthe bridge-plates with the rim
is disjunctive or conjunctive.

Acknowledgements
We are grateful to Dr A. Mclntyre for kindly providing uswith the filter sample~ studied here. We appreciate thehelpful comments ofDrs J.R. Young (NHM) and J.A. Lees

Discussion
Gephyrocapsa ericsonii (Plate 1, Figure 5) bears small
placoliths (<3J.lm in Iengtl1), each having two bridge-plates
that span tl1e central area, as observed in Gephy rocapsa
crassipons. Coccoliths of Reticu/ofenestra parvu/a var.
tecticentrum (Plate 1, Figures 6-8) do not have bridgeplates, but have a collar, the elements of which are oftenovergrown. This pattern of overgrowth can be misidentified
as bridge-plates. Therefore, it is plausible that G. crassipons
may have been misidentified as G. ericsonii or R. parvu/avar. tecticentrum in previous studies.
Okada & Mclntyre ( 1977) mentioned thatcoccoliths of G. crassipons differ from those of G. ericsonii
in the number of elements forming a bridge-plate, and in
the presence of a collar(= thickened inner tube). Although
no small Gephyrocapsa coccosphere with a combinationof coccolitl1s with thickened inner tubes(= G. crassipons)and with thin inner tubes (= G. ericsonii) have been
observed, the number of elements fonning a bridge-plate
is not consistent within a single coccosphere. Some
specimens possess both types of bridge-plates, i.e.
consisting of a single element or of several elements (Plate(UCL).

References
Hagino, K. & Okada, H. In prep. Horizontal di stribution ofcoccolithophore assembl ages in the equatori a l andsubequatorial Pacific Ocean.
Jordan, R.W., Broerse,A.T.C. , Hagino, K., Kinkel, H. , Sprengel,C., Takahashi, K. & Young, J.R. 2000 . Taxon lists for studies
of modern nannoplankton . Mar. Micropaleontol. , 39: 309314.
Okada, H. & Honjo, S. 1973 . Distribution of coccolithophorids
in the north and equatorial Pacific Ocean: Quantitative dataon samples collected during Leg 30, Oshoromaru, 1968 andLegHK694 , HakuhoMaru, 1969. WoodsHoleOceanography
Ins/., Tech. Rep orts, WHOI-73-81: 1-59.
Okada, H. & Mclntyre, A. 1977 . Modern coccolithophores of
the Pacitic and north Atlantic Oceans. Micropaleontol. , 23:1-55.

4

Journal of Nannolankton Research, 23, I , 200 I.

K. Hagino & H. Okada: Observations of Gephyrocapsa crassipons, p. 3-7.

Plate 1
Scanning electron micrographs of Gephyrocapsa crassipons, Gephyrocapsa ericsonii and Reticu/ofenestra parvula.
Scale bars indicate 1!UTI· Negatives of all photographs are archived in the Micropalaeontology Collection of the National
Science Museum, Tokyo. Numbers preceded by MPC are the specimen numbers in the collection.
Fig. I: Coccosphere of G. crassipons. Note distal shield equal in size to, or smaller than, proximal shield (arrows). MPC03696.
Fig.2: Etched specimen of G. crassipons. Note tube-core elements exposed between distal shield and inner tubeelements (arrow). MPC-03697.
Fig.3: Highly-overgrown specimen of G. crassipons. MPC-03698.
Fig.4: Highly-overgrown specimen of G. crassipons. Note degree of inward overgrowth of inner tube-elements varies
within single coccosphere. Central area of coccolith facing front completely covered by overgrown inner tubeelements (arrow). MPC-03690.
Fig.S: G. ericsonii. MPC-03700.
Fig.6: Weakly overgrown specimen of R. parvula var. tecticentrum . Note presence of two protruding collar-elements(arrows). MPC-03701.
Fig. 7: Moderately overgrown specimen of R. pan,ula var. tecticentrum . Note moderately overcalcified coccolith withpartly covered central-area (arrow a) and highly overgrown coccolith with completely covered central-area (arrow b).
MPC-03702.
Fig.8: Highly overgrown specimen ofR. pan,ula var. tecticentrum. MPC-03703 .

6

K. Hagmo & H. Okada: Observations of Gephyrocapsa crass1pons, p. 3-7.

Journal of armolankton Research, 23, I, 2001.

PLATE 1

G. crassipons

G. crassipons

G. crassipons

G. crassipons

G. ericsonii

R. parvula var. tecticentrum

R. parvula var. tecticentrum

R. parvula var. tecticentrum
7